Heat engine in the form of a water pulse-jet

ABSTRACT

A new heat engine in which liquid moves in a tube, one end of which is closed. The tube is heated at the closed end, and the liquid oscillates along the length of the tube. When the liquid interface enters the hot section, some of the interface vaporizes, so that the pressure in the space between the interface and the end of the tube increases, and the interface is forced back into the cooler section of the tube. The vapor then condenses, the pressure falls, and the liquid moves back toward the hot end. The longer the tube in relation to size of the hot section or &#39;&#39;&#39;&#39;boiler,&#39;&#39;&#39;&#39; the greater the momentum of the liquid when it enters the boiler, and the higher the peak pressure ratio which is developed. High pressure ratios are essential for efficient operation. It is also generally necessary for the boiler walls to be heavy enough to &#39;&#39;&#39;&#39;store&#39;&#39;&#39;&#39; the heat required for one complete cycle, and to be able to reject it to the water during the very short time that the interface is within the boiler. The engine as described is immediately applicable to boat propulsion. With variations, it can be applied to many other uses, including the production of shaft power and the pumping of fluids.

United States Patent [191 Payne 1 1 HEAT ENGINE IN THE FORM OF A WATERPULSE-JET [76] Inventor: Peter R. Payne, Box 282, Rt. 5,

Annapolis, Md. 21401 [22] Filed: May 8, 1973 [21] Appl. No.: 358,232

[52] US. Cl. 60/227; 60/221; 115/11; 1 15/12 R [51] Int. Cl B63h 11/12;F02k 7/02 [58] Field of Search 60/221, 227; 115/11, 12 R [56] ReferencesCited UNITED STATES PATENTS 789,641 5/1905 Weeks 115/11 1,200,96010/1916 McI-lugh... 46/95 1,480,836 l/1924 Purcell 60/227 1,787,844l/l93l Widdis 60/227 2,020,566 12/1935 Nelson 60/227 2,848,972 8/1958Orzynski... 115/1 1 2,885,988 5/1959 Myers 60/221 UX 3,013,384 12/1961Smith.... 60/221 X 3,079,751 3/1963 Lewis... 60/227 3,103,783 9/1963Smithm. 60/221 X 3,365,880 l/1968 Grebe 60/39.6 X 3,647,137 3/1972Naydan 60/221 FOREIGN PATENTS OR APPLICATIONS 443,255 2/1936 UnitedKingdom 115/11 602,034 5/1948 United Kingdom..... 115/11 478,917 l/l928Germany 60/227 347,591 l/l905 France 60/221 1 Aug. 12, 1975 PrimaryExaminer-Clarence R. Gordon Attorney, Agent, or Firm-Sughrue, Rothwell,Mion, Zinn & Macpeak [57] ABSTRACT A new heat engine in which liquidmoves in a tube, one end of which is closed. The tube is heated at theclosed end, and the liquid oscillates along the length of the tube. Whenthe liquid interface enters the hot section, some of the interfacevaporizes, so that the pressure in the space between the interface andthe end of the tube increases, and the interface is forced back into thecooler section of the tube. The vapor then condenses, the pressurefalls, and the liquid moves back toward the hot end.

The longer the tube in relation to size of the hot section or boiler,the greater the momentum of the liquid when it enters the boiler, andthe higher the peak pressure ratio which is developed. High pressureratios are essential for efficient operation. It is also generallynecessary for the boiler walls to be heavy enough to store the heatrequired for one complete cycle, and to be able to reject it to thewater during the very short time that the interface is within theboiler.

The engine as described is immediately applicable to boat propulsion.With variations, it can be applied to many other uses, including theproduction of shaft power and the pumping of fluids.

9 Claims, 14 Drawing Figures PATENTEU MM; 1 21975 3.898.800

SHEET 1 BOILER PATEIIIEII AUG I 2 m5 SHEET FIGIZ Fl G. I 3

EXPANSION a HEATING COMPRESSION SECTION SECTION COOLING SECTION E 4 R EI H G m H I N T B S F A Mm E mvAl l N AEL 0 VOLUME BETWEEN INTERFACE ANDBOILER END HEAT ENGINE IN THE FORM OF A WATER PULSE-JET BACKGROUND OFTHE INVENTION 1. Field of the Invention This invention relates to a newheat engine particularly adaptable for use with water as a working fluidand producing useful energy by the pulse-jet principle.

2. Description of the Prior Art 1 In boat propulsion, it is conventionalto start with a source of energy, e.g., fuel, which produces heat energyand to impart kinetic energy to the ambient water, so that the boat willbe pushed forward by reaction. It is usual to have a great deal ofmachinery between these two extremes. For example, the fuel heats waterin a boiler to make steam, which drives a turbine, which drives a waterpropeller via a gearbox, which develops a reactive thrust. In thepresent invention, the heat is applied directly to the ambient water in.order to achieve the same effect, thus eliminating the interveningmachinery. A known propulsive unit of this general type was patented byMcHugh in 1916 (US. Pat. No. 1,200,960), and the principle of his engineis illustrated in FIG. 1. Assuming that there is initially some water inthe boiler, the heat turns it to steam and pushes the ambient waterinterface down the tube. When all the water in the boiler has beenturned to steam, the steam condenses in the cool section of the pipe,the pressure drops, and the water interface moves back toward theboiler. When it reaches the boiler, some water splashes in, and becausethe tube is raised above the floor of the boiler, this splashed water istrapped and is again turned to steam, pushing the interface down thetube. A net thrust force to the left is produced, principally becausewhen the ambient water is flowing into the tube, it comes from alldirections (a sink flow) while when it emerges, it comes out as a jet,because finite fluid viscosity prohibits source flows from a pipe (seeFIG. 4). Numerous other later patents all operate on the same principleof trapping a small quantity of water in the boiler at the end of eachinduction phase.

McI-Iughs invention was specifically for a toy boat, and most of thefollowing inventors specify or imply the same application. It wasrecognized that the principle could not be scaled up to full scalelboatsprincipally because many people had attempted to accomplish this,particularly in the early 1920s, without success. There were two keyreasons for this inability to scale up the phenomena. Firstly, thesteam-water interface, shown in FIG. 1, was preserved by surfacetension, and this is only possible in very small diameter tubes. Inlarger tubes, there was no stable interface, and the steam bubbled intothe ambient water and was condensed without moving the bulk of the waterin the tube. More importantly, even if this problem had been solvable,the pressures developed were inherently low so that there was nopossibility of achieving efficient operation.

SUMMARY OF THE INVENTION In the present invention, illustrated in FIGS.2 and 3, the boiler is an integral part of the tube, and the momentumacquired by the water column as it moves toward the boiler is reliedupon to hold the interface in the boiler long enough to produce a usefulquantity of steam at high pressure. Stability of the interface betweenthe steam and the water is obtained because, for

most of the cycle, the water column is being accelerated toward theboiler. It is only accelerated away from the boiler when close to it oractually inside it, and this leaves very little time for the thenunstable interface to actually disintegrate.

A P-V diagram of the units operation is given in FIG. 14. For most ofthe cycle, the steam is condensing and the interface is slowing downfrom its initial rapid expulsion from the boiler. A condensing sectionis formally required, but in many practical cases, contact of theexhaust end of the tube with the ambient fluid is sufficient to providethis heat sink.

Since the fluid interface is in the boiler for only a very short periodof time, it is important that sufficient heat for one cycle be stored inthe boiler wall material, and that this heat be released to the waterrapidly. This implies either a material having high conductivity andhigh specific heat or a material having high conductivity andsubstantial weight.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic illustration ofthe prior art water pulse-jets.

FIG. 2 is a schematic illustration of the water pulsejet of thisinventionf FIG. 3 is another schematic illustration of the waterpulse-jet of this invention as applied to marine propulsion.

FIG. 4 is an illustration of the flow in and out of the open end of thetube.

FIG. 5 is a schematic illustration of one form of an air bleed.

FIG. 6 is a partial sectional view illustrating the exit end of the tubewith a bell-mouth design.

FIG. 7 is a schematic illustration of mechanically operated vanes todeflect the exhaust.

FIG. 8 is a schematic illustration of the use of a valve for modulatingthrust in the heat engine of this invention.

FIG. 9 is a schematic illustration of a water pulse-jet operable torecover ram pressure at high forward speeds.

FIG. 10 is-a schematic illustration of the use of an internal burner.

FIG. 11 is a schematic illustration of an embodiment in which acondenser or cooling jacket is positioned inside the boat hull.

FIG. 12 is a schematic illustration of a high specific heat boiler.

FIG. 13 is a schematic illustration of a boiler for extended steammaking.

FIG. 14 is a pressure volume diagram of the new cycle of this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 is a typical priorart construction in which heat is applied to a boiler and a .tubeextends upwardly into the boiler. The disadvantages of such aconstruction and its limitations and lack of ability to scale it up havesteam has condensed and the temperature of the remaining steam has beenlowered by virtue of being under the surface of water 24, the volume ofthe remaining steam contracts and the water-steam interface moves backto the left for additional water to be heated in the boiler.

FIG. 3 illustrates the invention as shown in FIG. 2 as applied to a boathull 26 operating in the water 24. Again, the tube 16 has a closed end18 to which heat is applied at a boiler section 20 and an open end 21for thrust propulsion as in FIG. 1.

FIG. 4 illustrates the problems with the open end 21 of the tube 16during the flow in and the flow out. During the flow in, there is aseparated flow region as illustrated.

Various means are contemplated within the scope of the invention tobleed trapped air or other gas from the closed end of the tube. One suchmeans is illustrated in FIG. 5.

The problem arises when air or other gas can become trapped in or nearthe boiler region of a pulse-jet. This may be due to the exhaust exitmomentarily coming out of the water; to a leak in the joint between thetube and boiler or elsewhere in the system; or because gas is boiled outof the water at the interface. In some engine configurations, as airleaks into the unit, or gas is boiled out, it collects near the end ofthe boiler and inhibits complete penetration of the boiler by theincoming interface. Eventually, after enough gas has accumulated, theunit stops operating entirely because the interface penetration of theboiler is so small that insufficient steam is generated to overcome thelosses and the work involved in expelling the exhaust water. Onesolution to this problem is to orient the unit so that the boiler isnear the lowest level, and most of the pipe inclines up toward theexhaust exit. (It can be sloped down again close to the exit.) Due togravity, the bubbles of gas will then work their way towards the exitand escape to the ambient water.

Another solution to this problem is provided by a pressure relief valvein the boiler which is spring loaded to remain closed below a certainpressure, but vents steam and air when that pressure is exceeded. Thedegree of venting is controlled by the force at which the valve opens.

Another way of venting trapped gas, illustrated in FIG. 5, is to run avery small diameter tube 28 from the top of the boiler to the ambientwater. This tube may be external to the pulse-jet or it may run insidethe main duct as shown. Gas at the top of the boiler flows into thistube when pressure is above ambient, and out when it is below. Becausethe flow in a small tube is laminar and because water-air interfaces arestabilized by surface tension, there is a net flow of the gas out of theboiler and down to the ambient water, so long as the unit is producingthrust; that is to say, so long as the integral of gauge pressure withrespect to time is positive.

The exhaust end 21 of the tube 16, may have a bellmouth shape 30 asillustrated in FIG. 6, and may have the holes 32 in its side, to reducelosses during the inflow stroke. If the Bell-mouth is not used, theintake flow shown in FIG. 4 causes separation just inside the tube,resulting in energy loss, and a reduction in the velocity at which theinterface approaches the boiler, so that less penetration is achieved.

For steering and reversing purposes, mechanically or power-operatedvanes 34, 36, as shown in FIG. 7, permit deflection of the exhaust.These are located far enough downstream from the nozzle so as not tointerfere with the intake flow. A distance of one diameter is usuallysufficient. If FIG. 7 is a top plan view, then the vanes are shownpositioned to deflect the jet in such a way as to cause the boat to turnto the left. If both vanes come aft to meet behind the exhaust, thenreverse thrust is obtained.

A thrust modulation valve 38 shown in FIG. 8 (shown in a closedposition) may be provided and is opened by steam pressure. Assuming thatthe unit is charged, the water above the valve is trapped until thesteam pressure rises above a certain preset value. This preset value canbe applied with a spring, for example. WHen the pressure exceeds thisvalue, a piston 40 opens the valve and the unit discharges. In practice,it generally recharges itself before the spring has time to reclose thevalve, but in some cases where the valve inertia and friction are verylow, it is necessary to mount a damper or time-delay device on thevalve. The advantage of this valve is that the unit will still operatewhen the heat input to the boiler is too low for conventional(valveless) operation, or if the boiler is too light to store the heatrequired for one cycle.

The water pulse-jet of this invention may be provided with a forwardfacing intake. A unit is shown in FIG. 9 which accepts induction waterfrom ahead through inlet 42 and expels it astern, thereby taking fulladvantage of the ram water pressure in the induction phase.

A two position valve 44 (self operating) may be utilized as a ramrecovery valve. Alternatively, it is belleved that a system may beprovided in which three position valve is driven by an external motor inaccordance with signals from a logic circuit which determines theoptimum valve position. The logic circuit would be connected to one ormore pressure or temperature sensors in the unit so that the location ofthe interface would be known.

FIG. 10 shows this invention with internal heating means, i.e., apulse-jet in which the heat is supplied from a flame within the boiler.Because of its location, burner 46 must be supplied with air as well asfuel. This can be done by pressurizing air and fuel to force them intothe unit through tubes 48 and 50, respectively, or

by allowing the low pressure which exists in the unit for part of thecycle to draw them in through non-return valves. The insoluble gasesresulting from combustion are bled off, using one of the bleedertechniques described earlier.

When the fuel and air are supplied under pressure, it is predicable thatsome improvement in performance could be obtained by pulsating them sothat little or no heat is added when the interface is away from theboiler, while the flame is at its maximum heat setting when theinterface is in the boiler.

In order to obtain very quick starts, it may be advantageous tosubstitute oxygen for air for the first few seconds of the pulse-jetsoperation, so that steam is made very rapidly. Substitution of oxygenfor air can also be used as a booster when it is required to increasethe thrust output of the unit temporarily.

The embodiment shown in FIG. 10 also differs from the previouslydiscussed embodiments in that it utilizes heat storage baffles 52. I

A condenser or cooling jacket as indicated in FIG. 11 may be used topromote condensation. The cold water supply 54 to the water jacket 53may be from a pump or it may be induced by the motion of the boatthrough the water. Sliding such a water jacket towards the boiler wouldin general increase the frequency of operation, but reduce the thrust ofthe unit, so that movement of the water jacket 53 can be used as amethod of thrust control.

In all external heating schemes and with internal heating when the flameis not pulsed, most of the heat for one cycle has to be stored in theboiler wall and given up during a very short period, during which theinterface is in the boiler. Metals having high specific heats (C aretherefore desirable. Examples are tin (C,, 0.55) and lithium (C,= 0.79),as compared with copper, for which C,, is only 0.1. Because of their lowmelting points, the use of such metals in a boiler requires that it bejacketed. An idealized scheme is illustrated in FIG. 12 where highspecific heat metals 56 are jacketed by highly conductive metals 58.

As in all other cases, the boiler may contain fins such as the heatstorage baffles 52 shown in FIG. to better conduct the heat from the hotboiler material to the water and steam.

Means of trapping a small quantity of water in the boiler after theinterface has left, such as the grooves 60 in FIG. 13, so that steam isstill made after the interface leaves the boiler may be used for steammaking. The size of the trap is adjusted to ensure that all of thetrapped water is boiled before the first part of the condensation cycleis complete, and the interface starts to return to the boiler. Incertain configurations, such water traps can increase the thrust of theunit, for a given heat input.

FIG. 14 is an idealized P-V diagram for the cycle of this new engine. Asthe steam condenses, the inertia of the water rushing back toward theheating section carries the water well into the heating zone where itflashes into steam and the pressure builds very rapidly as shown on theleft hand side of FIG. 14. The high pressure steam arrests the movementof the water and accelerates it rapidly back in the other direction,which constitutes the expansion phase. The expansion is a little betterthan adiabatic because some heat is still being added to the steam bythe boiler. When the water interface reaches the cooling section, steamstarts to condense and the pressure falls. Despite the rapid fall off inpressure, the momentum of the water carries it well down into thecooling section so it is possible for virtually all of the steam tocondense resulting in a very low pressure.

The starting procedure for a water pulse-jet (which is notself-starting, as some are) is as follows:

When the boiler is the highest part in the system, starting the unit canpresent difficulties. The boiler warms up, steam is made, and theinterface moves down away from the boiler until a position ofequilibrium is reached where the heat in is balanced by the heat out. Ifthis happens, it is necessary to perturb the interface in some way inorder for the unit to commence oscillating. A small piston, pushed upthe tailpipe and then pulled out rapidly will achieve this, as will manyother devices which will be obvious to those skilled in the art. Forexample, admission of a small quantity of cold water closeto the boiler,cooling the outside of the pipe with cold water, use of a pyrotechniccharge, and so on.

While the requirements for the boiler have been described above, it isstill necessary to define the best material for the tube itself. Ingeneral, that portion of the tube which sees either steam or water,depending on the position of the interface (that is to say, from theboiler proper down to a location at least halfway along the tube), thematerial should be 1. A poor conductor so that heat is not carried awayfrom the boiler and dissipated uselessly in the water behind theinterface;

2. A poor absorber of heat so that it does not extract heat from thesteam too quickly.

One way of avoiding boiler heat loss along the tube is to introduce aninsulated section close to the boiler, which effectively blocks any heatflow. An easier solution, although somewhat less efficient, is the useof thin-walled stainless steel tube, since this is a relatively poorconductor of heat. Other solutions are to coat the inside of the tubewith a ceramic having the desired low absorption and low conductivitycharacteristics.

When the interface enters the boiler and is arrested, very high peakpressures can be developed, and in some configurations, these can behigh enough to cause failure of either the boiler or the joint betweenthe boiler and the pipe. The peak pressures are principally associatedwith the interface striking the top end of the boiler, and they may bealleviated by 1. Increasing the length of the boiler so that enoughsteam is made to arrest the interface before reaching the end;

2. Introducing some trapped gas into the boiler;

3. Mounting either the boiler or the entire unit resiliently withrespect to the structure to which it is attached.

An example of the latter is a short section of rubber hose between theexhaust exit and the main portion of the pulse-jet pipe. Each time theunit experiences the peak pressure pulse, the hose stretches, allowingthe entire unit to move forward and cushion the shock.

Water pulse-jets so far built have circular tubes and boilers forconvenience. In principle, the duct can be of any shape and crosssection that is convenient, although a circular section is to bepreferred at the boiler and close to it because of the high pressuresdeveloped. The duct can also be coiled for compactness of installationor bent into any convenient shape, so long as it is remembered that eachsharp bend causes a loss in efficiency. In some cases, the gyroscopicmoment associated with the water flow in coiled ducts will give asteadying action to a boat in waves. The cross-sectional area of theduct and boiler can also change longitudinally.

If an outlet 21 is uncovered (by a motion of the boat in waves, forexample) some water will ordinarily drain out of the unit or air will bedrawn in, depending on where in the cycle this event occurs. Three meanswhich is believed could be used to alleviate this problem are asfollows: i

1. A water height sensor could be connected to an electric motor sothat, when the unit is within a certain critical distance of thesurface, water is force fed to the pulse-jet from the side, so there isa constant outflow, and no room for air to enter.

2. An exhaust valve could be connected to a buoyant element whichnormally holds the exhaust valve open, but which closes when the watersurface approaches the pulse-jet exit.

3. A valve could be provided in the unit, near the exit, which wouldshut off the unit entirely on receipt of a signal from a local waterheight sensor, and a second valve could be provided which would vent theboiler steam (at pressure) until the exhaust nozzle was back in thewater. The logic network connected to the water height sensor could alsocut back fuel flow to the heater during this shutdown period.

It is believed that a boiler could have a valve along its length so thatonly part of the boiler would be available to the water when operatingat low thrust or at low forward speed. When the craft was moving athigher speeds, so that ram pressure (e.g., FIG. 9) provides more impetusfor incoming flow, the valve could be opened to permit the full lengthof the boiler to be used in making steam. A multiplicity of such valvescould be used to permit optimization of boiler length for various speedsthrough the water. I

Various means of heating other than the burners described could probablybe used. Several such meansare set forth below. i

A lens to focus the suns rays on the boiler, in order to provide all orpart of the necessary heat for the pulse jets operation, could beutilized.

Instead of the boilers discussed so far, a heat exchanger which permitsthe coolant of an atomic pile to give up heat to the water each time thewater enters the heat exchanger and hence operate the pulse-jet may beused. Such a system would be advantageous for use in atomic submarines,for example. Some isotopes can maintain a temperature in the range300'600F. for periods in excess of a month, and hence provide thenecessary power for a pulse-jet. The isotopes may be mounted inside theboiler, or the boiler wall itself may be coated with or manufacturedfrom the isotope.

THe foregoing discloses in detail the application of this new cycle to aparticular problem, that of marine propulsion But it will be understoodthat this new heat engine cycle can be applied in many other ways, toproduce fluid or mechanical power from heat. That is to say, it can actas a pump or an engine. If water, or any other suitable fluid, istrapped in a pulsejet by a piston, with an appropriately located waterjacket for the condensing section, it will cause the piston to oscillateand do work. The same configuration could be 'used to make a piledriver. On a separated intake-exit unit, such as that illustrated inFIG. 9, one could connect a reservoir of fluid to the inlet and use thewater pulsejet to pump this fluid through the exhaust exit. Such a unitwould be advantageous for producing a jet of water for fire fighting,for example. Small such units, equipped with reservoirs, could be usedas water guns. Their nozzle velocity could be increased by multistaging,whereby one pulse-jet element discharges the liquid into a second andfrom thence to a third, kinetic energy being added at each cycle untilthe liquid is finally discharged.

A separate inlet-exit pulse-jet can act as a pump to both heat and pumpwater around'a hot water heating system. Operating the water columnagainst an air or other spring, a water pulse-jet could be used as asteam generator.

In describing the present invention, water is referred to as the workingfluid. However, any working fluid capable of changing from liquid tovapor on the application of heat may in principle be used.Alternatively, a trapped gas could be used as the working fluid, inwhich case it is notnecessary for the fluid to'vapori ze.

Although one heat engine has been shown'and described, it is withinthescope of this invention to gang a plurality of such engines andsynchronize their outputs in staggered fashion.

I claim:

1. A heat engine comprising:

a. a tubular member, said tubular member being completely closed at oneend and open at the other to a source of working fluid such that theworking fluid has access to said tubular member through the open endthereof,

b. heating means for heating the working closed end of said tubularmember;

c. a material having high specific heataround the closed end of saidtubular member to store heat;

(1. a jacketing material having high heat conductivity arranged aroundsaid material having high specific heat; and I e. cooling means forcooling said tubular member adjacent the open end thereof,

whereby, when said heating means are functioning during use of the heatengine, the working fluid has a liquid and a vapor phase and the workingfluid oscillates within the tube as it is alternately vaporized by saidheating means and condensed by said cooling means, thereby producinguseful power. v

2. A heat engine as recited in claim 1 wherein said jacketing materialmakes up at least a portion of the closed end of said tubular member.

3. A heat engine as defined in claim 2 which operates on the P-V cycleof FIG. 14. I

4. A heat engine as in claim 2 wherein the working fluid is water.

5. A heat engine as in claim 2 wherein the walls of the tubular member.store sufficient energy for one cycle.

6.,A heat engineias in claim 2 wherein the tubular member is circular insection. v

7. A heat engine as in claim 2 wherein the walls of the tubular memberadjacent to closed end are of a material having high conductivity andhigh specific heat or substantial weight. v

8. A heat engine as in claim 3, wherein the open end of the tubularmember is immersed in the water.

9. A heat engine as in claim 2, wherein the tubular member has aninternal diameter sufficiently large so that the surface tension of theworking fluid in its liquid phase does not stabilize a liquid-vapo rinterface of the working fluid within the tubular member, said interfacebeing stabilized both by momentum of the working fluid in its liquidstate as it moves toward the closed end ofthetube.

1. A heat engine comprising: a. a tubular member, said tubular memberbeing completely closed at one end and open at the other to a source ofworking fluid such that the working fluid has access to said tubularmember through the open end thereof; b. heating means for heating theworking fluid at the closed end of said tubular member; c. a materialhaving high specific heat around the closed end of said tubular memberto store heat; d. a jacketing material having high heat conductivityarranged around said material having high specific heat; and e. coolingmeans for cooling said tubular member adjacent the open end thereof,whereby, when said heating means are functioning during use of the heatengine, the working fluid has a liquid and a vapor phase and the workingfluid oscillates within the tube as it is alternately vaporized by saidheating means and condensed by said cooling means, thereby producinguseful power.
 2. A heat engine as recited in claim 1 wherein saidjacketing material makes up at least a portion of the closed end of saidtubular member.
 3. A heat engine as defined in claim 2 which operates onthe P-V cycle of FIG.
 14. 4. A heat engine as in claim 2 wherein theworking fluid is water.
 5. A heat engine as in claim 2 wherein the wallsof the tubular member store sufficient energy for one cycle.
 6. A heatengine as in claim 2 wherein the tubular member is circular in section.7. A heat engine as in claim 2 wherein the walls of the tubular memberadjacent to closed end are of a material having high conductivity andhigh specific heat or substantial weight.
 8. A heat engine as in claim3, wherein the open end of the tubular member is immersed in the water.9. A heat engine as in claim 2, wherein the tubular member has aninternal diameter Sufficiently large so that the surface tension of theworking fluid in its liquid phase does not stabilize a liquid-vaporinterface of the working fluid within the tubular member, said interfacebeing stabilized both by momentum of the working fluid in its liquidstate as it moves toward the closed end of the tube.